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T. RIGBY. TREATMENT OF WET CAR BONIZED PEAT OR THE LIKE.

APPLICATION FILED .IULY [1.19M-

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Patented Aug. 8, 1916.

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T. RIGBY.

TREATMENT OF WET CARBONI ZED PEAT OR THE LIKE..

APPLICATION FILED JULY 11.1914.

1 1 93,924. Patented Aug. 8, 1916.

2 SHEETS-SHEET 2- Witnesses:

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THOMAS RIGBY, OF DUMFRIES,

SCOTLAND, ASSIGNOR TO WETCARBONIZING LIMITED, 01'! LONDON, ENGLAND.

TREATMENT OF WET CARBONIZED PEAT OR THE LIKE.

Specification of Letters Patent.

Patented Aug. 8, 191 6.

Application filed July 11, 1914. Serial No. 850,483.

To all whom it may concern:

Be it known that I, THOMAS RIG Y, a subject of the King of Great Britain and Ireland, and a resident of 61 Loreburn street, Dumfries, Scotland, have invented certain new and useful Improvements in and Relating to the Treatment of Wet Carbonized Peat or the like, of which the following is a specification.

This invention relates to the dewatering of peat the water of which has at least in part been rendered free in the mass by heat treatment as by the Ekenberg heat carbonizing process or the newer forms thereof. It is known that dewatering of such material is most economically and reliably-effected in two distinct stages, the first being a filter pressing operation to produce cakes of partly dried material and the second either a waste heat drying method or a mechanical method such as pressing in a band press, these latter alternative treatments being rendered economically possible by the solidity given to the material in the initial filter pressing operation. The use of filter presses of the ordinary type however presents certain disadvantages from the standpoint of opening and discharging the press chambers and renders it desirable to efiect if possible the filter pressing by some more convenient means.

I have as the result of experiments ascertained that under certain circumstances, peat which has by heat treatment of the kind referred to had its water freed, can, by even that slight pressure which can be applied by suction, be easily dewatered in a-relativelyshort time not of course to the same degree as in a filter press, but nevertheless to a sufficient degree to give it the necessary solidity for after treatment in presses or driers of the character indicated. This result can be attained with fairly thick masses and mere films are not required to be used so that continuous filtering devices, 6. g. of the vacuum type with automatic charging and discharge and capable of giving a sufficient output for practical purposes become available. On the other hand undue thickness must be avoided and beyond certain limits the effect of suction is insufficient for practical purposes.

In experiments of one particular class of peat of a somewhat fibrous character, I have ascertained that at a vacuum of 34 cm. of mercury or at any greater vacuum the dewatering of a peat pulp wetcarbonized while containing upward of 90% of water can be carried to a water content of some 7580%, and this with thicknesses of final cake of up to nearly an inch. At this water content the material had a certain solidity and the dewatering occupied a short while only (a few seconds in the case of a cake several millimeters thick) this time increasing approximately as the square of the final thickness. For instance, to reduce the peat to a water content of 80% in a film 0.3 cms. in thickness required the application of a vacuum of 345 cms. at a temperature of some 50 C. for only 10 seconds but in a film some 1.7 ems. in thickness required about 3.1; minutes. The use of a vacuum above 3 f cms. did not apparently give any proportional benefits nor did the temperature at which filtration was conducted do more than affect the rate of loss of water. According to the present invention therefore the peat is subjected to filtration in relatively thin masses under the influence of just sufiicient pressure and preferably by suction to render it sufficiently plastic to permit of its after-treatment in a mechanical press such as a band press, or its disintegration and desiccation in hot combustion gases or other drying process.

Referring now to the accompanying drawingsFigure 1 shows in sectional elevation a vacuum filter suitable for carrying out the above process, while Figs. 2 and 3 show in sectional elevation and plan respectively a complete plant for dewatering the peat in two stages.

In carrying out the invention with the filter shown in Fig. 1, the wetcarbonized peat pulp while still at a sufficiently high temperature to insure rapid loss of its water, is distributed from a pipe 66 in a thin layer over a filtering surface 6 carried by a circular table 0, which is rotated through gearing d and e by an electric motor f. The space between the filtering surface Z) and the bottom of the table 0 is divided up by radial partitions 9 into segmental chambers h, which can be evacuated by suitable pumps connected through a fixed pipe 70. In this way, dewatering of the peat is effected while the latter is being carried around. by the table 5, which is caused to rotate at such a rate that by the time the layer reaches a scraper conveyer m by which it is removed, the material has been dewatered to the desired extent. The efliuent thus expressed by means of gearing g, in order that the en-- tire filtering surface may be so treated. When additional dewaterlng is to be effected in a band press, the plant 1s arranged as illustrated in Figs. 2 and 3, in elevation and plan respectively. The filter-pressed material is delivered by the scraper conveyer on into a plug mill 1, and passed from thence by a screw conveyer between the bands 8' of the band press, the pressure in which is adjusted by altering the angle between two endless roller bands 25, whose position can be adjusted by hydraulic pistons operating in cylinders a. In cases where the further dewatering is to be effected by drying in waste flue gases, the filter shown in Fig. 1 may be inclosed to permit application of a slight pressure on the upper side of the filtering surface Z) by increasing the pressure of the superin'cumbent gaseous medium.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is 1. A process for dewatering peat consisting in subjecting a wet pulp of the peat to digestion under pressure sufiicient to prevent ebullition until its water is rendered freely expressible, spreading the treated pulp in a thin layer, dewatering such layer by suction applied thereto until it has acquired by v1rtue of loss of water sufficient solidity for handling as a solid, and thereafter subjecting it to a further dewatering process.

2. A process for dewatering peat consisting in digesting a wet pulp of it by heat without evaporation untilits-Water has been unbound, continuously converting the treated mass into a thin layer in contact with a filtering surface, subjecting the continuously formed layer to pressure created by a vacuum, maintaining such pressure until the material has acquired enough solidity for handling as a solid, and thereafter subjecting the solid to a further drying operation.

3. A process for dewatering peat consisting in converting it into a wet pulp, digesting the wet pulp at an elevated temperature and under pressure suflicient to prevent ebullition until its water binding properties are destroyed, removing water from a continuously formed thin layer of the material by suction until the material has acquired solidity, and thereafter dewatering the material further as a solid.

i i. A process of dewatering wetcarbonized peat plup, consisting in automatically and continuously distributing the treated pulp as a thin layer upon a. filtering'surface, dewatering said pulp by pressure produced by a vacuum under said surface until the material contains some 75% to 80% of water, likewise automatically and continuously removing said pulp from said surface and thereafter dewatering it by high pressure applied. thereto while in a suitably spreadout condition; as set forth.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

' T. RIGBY.

WVitnesses BERTRAM H. MATTHEWS, H. DUNWORTI-I.

copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. C. 

